At present, there is practically used a fuel cell system which generates electric power by supplying fuel gas to an anode electrode of a fuel cell and oxidizing gas to a cathode electrode and causing an electrochemical reaction. In a fuel cell of such fuel cell system, since heat is generated during the electrochemical reaction (power generation), the power generation efficiency may be reduced by the heat. For this reason, by providing a cooling mechanism for cooling the fuel cell, the operating temperature of the fuel cell is maintained to a suitable temperature range to thereby suppress the reduction of the power generation efficiency.
As a conventional cooling mechanism, there is proposed a type which is constituted by a coolant passage for circulating coolants (cooling water and the like) into a fuel cell, a pump for circulating the coolant, a radiator and a fan for cooling the hot coolant discharged from the fuel cell, a temperature sensor for detecting a temperature of the coolant, a control device for controlling the pump and the fan on the basis of the detected coolant temperature, and the like.
Further, in recent years, there has been proposed a technique which detects a temperature (inlet temperature) of a coolant flowing into a fuel cell and a temperature (outlet temperature) of the coolant discharged from the fuel cell by temperature sensors, and which detects abnormality of a cooling mechanism and controls a flow rate of the coolant on the basis of the detected temperatures (see, for example, a Japanese Patent Laid-Open No. 2003-109637). By adopting such technique, it is possible to adjust the temperature of the fuel cell on the basis of the inlet temperature and outlet temperature of the coolant.